The following abbreviations are defined as follows:    DCH Dedicated Channel    DPDCH Dedicated Physical Data Channel    DPCCH Dedicated Physical Control Channel    EDCH Enhanced Uplink DCH    E-DPDCH Enhanced DPDCH    E-RNTI EDCH RNTI    HARQ Hybrid Automatic Repeat Request    HSUPA High Speed Uplink Packet Access    IE Information Element    MAC-e Enhanced Media Access Control    Node B Network Node, eg., a Base station    RNC Radio Network Controller    RNTI Radio Network Temporary Identifier    RRC Radio Resource Control    SG Serving Grant    UE User Equipment, eg., a mobile terminal
of interest herein is the uplink DCH (EDCH) for packet data traffic in, for example, Release 6 of 3GPP TS 25.309, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; FDD Enhanced Uplink; Overall Description; Stage 2 (Release 6).
In HSUPA, attempts at enhancements are currently approached by distributing some of the packet scheduler functionality to the Node Bs to provide faster scheduling of bursty, non-real-time traffic than can be provided by the Layer 3 (L3, Network Layer) of the RNC. The principle animating this approach is that, with faster link adaptation, it is possible to more efficiently share the uplink power resource between packet data users. For example, when packets have been transmitted from one user the scheduled resource can be made available immediately to another user. This technique attempts to avoid the peaked variability of noise rise, such as when high data rates are being allocated to users that are running bursty high data-rate applications.
In the current architecture the packet scheduler is located in the RNC. As a result, the packet scheduler is limited in its ability to adapt to the instantaneous traffic due at least in part to bandwidth constraints on the RRC signaling interface between the RNC and the UE. Hence, to accommodate the variability, the packet scheduler must be conservative in allocating uplink power to take into account the influence from inactive users in the following scheduling period. However, this solution has been found to be spectrally inefficient for high allocated data-rates and long release timer values.
With EDCH, much of the packet scheduler functionality is transferred to the Node B, i.e., there is a Node B scheduler that takes care of allocating uplink resources, including controlling the SG of the UE.
Each time the UE enters a new cell, it receives the SG either from the RNC through RRC signaling, or from the serving Node B via Layer 2 (L2, data link layer) signaling (absolute grant channel).
However, when the UE moves from one cell to another there is no simple means for the SG to be maintained. This makes service continuity difficult and limits the HSUPA in its ability to efficiently support services with guaranteed bit rates.
Further, from the received data the RNC can assess the value of the scheduled grant and, when the cell is changed, it can include that value in the RRC signaling. However, since the SG is given in terms of maximum E-DPDCH to DPCCH power ratio that the UE is allowed to use for scheduled data, such an assessment is not straightforward for the RNC and may be subject to large error. In other words, it is difficult for the RNC to assess the value of the SG being used by the serving cell and, consequently, it is also difficult for RNC to maintain the correct value of the SG during a cell change.